We can just use the generic rule to determine block partitions:
If it is listed in /proc/partitions, it's a partitionable device
or a partition. The partition delimiter is 'p' if the disk name
ends with a number, otherwise the numbers follows the last letter
is the partition number.

use the fstab device name if stat shows the same major and minor as the fstab device (fixes vmware)
fix vol_id call to use a device node
fix fallback_rootdev to not resolve the rootdev (fixes double Root-line as well)